Introduction to Pulmonary Sequestration and Rare Malignancies

Pulmonary sequestration is a rare congenital lung malformation defined by non-functioning lung tissue that lacks normal communication with the tracheobronchial tree. Specifically, this tissue receives its blood supply from the systemic circulation rather than the pulmonary arteries. Physicians typically classify these anomalies as either intralobar or extralobar based on their pleural coverage. While clinicians usually consider these lesions benign, they can harbor life-threatening complications like recurrent infections or massive hemoptysis. However, the development of a pulmonary sequestration melanoma represents an exceptionally rare event in thoracic oncology. Historically, the medical literature has documented adenocarcinomas as the most frequent malignancy found within sequestered lung segments. Consequently, identifying a melanoma in this setting challenges current understanding of oncogenesis in congenital lung malformations. This case report introduces the first known instance of such a presentation, emphasizing the need for comprehensive diagnostic evaluation in elderly patients. Practitioners must maintain a high index of suspicion when previously stable lesions demonstrate new morphological changes. Therefore, understanding the potential for rare neoplasms within sequestration is vital for modern pulmonology and thoracic surgery. This discovery expands our clinical perspective on the biological potential of sequestered tissues and their long-term surveillance requirements.

Clinical Presentation and Diagnostic Evolution

An 84-year-old male patient originally received a diagnosis of intralobar pulmonary sequestration two years before his surgical intervention. Initially, multislice computed tomography (MSCT) identified the lesion in the left lower lung lobe, showing an anomalous arterial supply originating from the thoracic aorta. For two years, the patient remained stable until he presented to the emergency department with recurrent hemoptysis. This symptom progression significantly altered the clinical trajectory and necessitated immediate surgical consultation. Another MSCT scan performed during this period revealed a newly formed solid lesion within the previously described sequestration. This radiological evolution is a critical red flag for malignancy in any congenital lung anomaly. In addition, the patient's age and the sudden onset of symptoms suggested an aggressive underlying process. Thoracic surgeons decided to proceed with surgical resection to address the hemoptysis and investigate the nature of the solid mass. Such cases demonstrate how symptoms like hemoptysis often serve as the primary indicator for occult malignancy in long-standing sequestration. Furthermore, the transition from a stable cystic or solid-cystic lesion to a rapidly changing mass requires definitive tissue diagnosis through resection. This patient’s journey highlights the unpredictable nature of adult pulmonary sequestration and its potential for late-life complications.

Radiographic Identification and Surgical Strategy

Effective management of pulmonary sequestration relies heavily on advanced imaging modalities like MSCT and PET/CT. In this case, the MSCT scan provided the gold standard for identifying the anomalous systemic artery, which is essential for safe surgical planning. Without precise identification of these vessels, surgeons risk catastrophic bleeding during lobectomy. Therefore, the surgical team performed a left lower lobectomy and systematic lymphadenectomy via thoracotomy. This approach ensures complete removal of the sequestered tissue and the associated malignancy while providing adequate nodal staging. Specifically, the surgeon must carefully ligate the systemic arterial supply, which often exhibits high pressure and fragile walls. In this instance, the newly discovered solid lesion within the sequestration drove the decision for a radical lobectomy over a simpler segmentectomy. Moreover, systematic lymphadenectomy remains mandatory whenever clinicians suspect primary lung cancer or rare neoplasms. Post-operative recovery generally depends on the patient's age and baseline pulmonary function. This case underscores that surgical intervention remains the treatment of choice for symptomatic or changing pulmonary sequestrations in adults. Ultimately, a combination of precise radiographic mapping and aggressive surgical resection provides the best chance for diagnosis and symptom control in such complex presentations.

Histopathological Analysis of Pulmonary Sequestration Melanoma

Post-operative histopathological analysis yielded surprising results by discovering two distinct melanomas within the resected specimen. The larger lesion measured 6 cm in its greatest dimension, while the smaller one measured 1.7 cm. This pathological finding was unprecedented, as the pulmonary sequestration melanoma had never been reported in medical literature. Specifically, the analysis confirmed the presence of malignant melanocytes within the sequestered lung tissue, which typically lacks such cell types. Pathologists faced the significant challenge of determining whether these were primary pulmonary lesions or metastatic spread. To investigate further, clinicians performed a thorough skin examination and excised several suspicious skin lesions. However, none of the biopsied skin samples showed evidence of melanoma, increasing the likelihood of a primary pulmonary origin. Additionally, a PET/CT scan conducted after the surgery found no other signs of malignant disease elsewhere in the patient's body. These findings are crucial because primary pulmonary melanoma only accounts for approximately 0.01% of all lung tumors. Consequently, finding such a rare tumor within a congenital malformation like sequestration adds a layer of extreme complexity to the case. This specific pathology highlights the importance of detailed immunohistochemical staining, including markers like S-100, HMB-45, and Melan-A, to confirm the melanocytic nature of the cells.

Differentiating Primary from Metastatic Pulmonary Melanoma

The distinction between primary pulmonary melanoma and metastatic disease from an occult or regressed primary site is notoriously difficult. Specifically, the Jensen criteria traditionally help clinicians establish a primary diagnosis, requiring the absence of prior melanoma history and no extrapulmonary involvement. In this case, the negative PET/CT and skin biopsies supported the possibility of a primary lesion arising within the sequestration. However, the origin of melanoma within the lung remains controversial, with some theories suggesting that melanocytes migrate to the respiratory tract during embryogenesis. Others propose that pluripotent stem cells within the lung tissue undergo melanocytic differentiation. Regardless of the exact histogenesis, the presence of two separate nodules in this patient complicated the staging and prognosis. Unfortunately, the disease disseminated one year after the surgery, reflecting the aggressive biological behavior of malignant melanoma. This outcome emphasizes that even with successful surgical resection, the long-term prognosis for pulmonary melanoma remains poor. Furthermore, this case demonstrates that pulmonary sequestration may serve as a niche for rare neoplastic development, requiring lifelong vigilance. Clinicians must consider the possibility of spontaneous regression of a primary skin lesion when encountering pulmonary melanoma. Therefore, a multidisciplinary approach involving dermatologists, oncologists, and pathologists is essential for navigating these diagnostic dilemmas.

Conclusions and Clinical Implications for Practitioners

This landmark case provides several critical lessons for the global medical community regarding the management of congenital lung malformations. First, it demonstrates that pulmonary sequestration is not purely a benign entity and can indeed harbor aggressive malignancies like melanoma. Second, any new solid components identified within a stable sequestration must be treated as suspicious for cancer until proven otherwise. Consequently, thoracic surgeons should lean toward resection in symptomatic adults or those showing radiological progression. Moreover, the diagnostic challenge of distinguishing primary from metastatic melanoma requires a comprehensive workup, including whole-body PET/CT and thorough skin evaluations. While surgery provides local control and essential diagnostic tissue, systemic recurrence remains a significant threat. Physicians must therefore provide realistic prognostic counseling to patients diagnosed with rare pulmonary neoplasms. This report highlights that our current understanding of the potential for malignant transformation in sequestration is still evolving. Future research should focus on the molecular pathways that lead to such rare presentations. Ultimately, maintaining a high clinical suspicion and pursuing definitive surgical management remains the best strategy for ensuring patient safety. This case serves as a vital reminder that rare presentations can occur even within common congenital anomalies, requiring a meticulous and evidence-based clinical approach.

Frequently Asked Questions

How is pulmonary sequestration typically diagnosed in modern clinical practice?

The gold standard for diagnosing pulmonary sequestration is multislice computed tomography (MSCT) with intravenous contrast. This imaging modality allows clinicians to visualize the hallmark anomalous systemic arterial supply originating from the aorta. Furthermore, MSCT provides excellent anatomical detail of the non-functioning lung tissue and its relationship to the normal bronchopulmonary tree, which is essential for planning safe surgical interventions or embolization procedures.

Why is surgical resection recommended for adults with pulmonary sequestration?

Surgical resection is primarily recommended for adult patients to prevent recurrent infections, treat hemoptysis, and exclude occult malignancy. Studies indicate that nearly 11% of adult congenital lung malformations may harbor tumors, such as adenocarcinomas or rare melanomas. Consequently, removing the sequestered tissue eliminates the source of chronic inflammation and provides a definitive diagnosis, thereby reducing the long-term risk of malignant transformation and other life-threatening pulmonary complications.

What are the primary challenges in diagnosing primary pulmonary melanoma?

Diagnosing primary pulmonary melanoma is challenging because clinicians must exclude metastatic disease from an occult or regressed primary skin lesion. Pathologists use specific immunohistochemical markers like HMB-45, S-100, and Melan-A to confirm the diagnosis. However, because primary pulmonary melanoma represents only 0.01% of lung cancers, most cases are initially suspected to be metastatic. A thorough workup involving PET/CT scans and detailed dermatological examinations is mandatory to support the diagnosis.

Disclaimer: This content is for informational and educational purposes only and does not constitute medical advice. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Refer to the latest local and national guidelines for clinical practice.

References

Bečejac T et al. Malignant melanoma identified within a pulmonary sequestration- a case report. J Cardiothorac Surg. 2026 Jul 19. doi: 10.1186/s13019-026-04594-9. PMID: 42471742.

StatPearls. Pulmonary Sequestration. [Online]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441893/

Seitelman E et al. Successful treatment of primary pulmonary melanoma. J Thorac Dis. 2011;3(3):207-208. doi: 10.3978/j.issn.2072-1439.2011.02.04.